Abstract
In all tracheophytes, the flow of both xylem and phloem sap is driven by gradients in hydrostatic pressure generated at the transport endpoints. However, this long-distance transport is founded upon a vast underlying layer of local material exchange between xylem, phloem, and the surrounding tissues operating at length scales of no more than a few millimeters. As such, the control of transport in tracheophytes involves a radical juxtaposition of large- and small-scale processes, where the “decision making” done locally by the units that compose the transport pathway is relatively autonomous, but their combined activity is beneficial to the plant as a whole. This strong role for local control of xylem and phloem transport means that the “conduit” portion of the vasculature cannot be viewed as a silent partner subservient to the needs of the transport endpoints. This chapter discusses the physiology of the xylem and phloem and the interactions between them in relation to their use of potassium to internally regulate transport function in heterogeneous environments.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
